Following the “horror of Fredericksburg” (December 13, 1862), the Confederate army of Gen. Robert E. Lee and the Union force under Gen. Joseph Hooker had spent the winter facing each other across the Rappahannock River in Virginia. On April 27 Hooker dispatched his cavalry behind Lee’s army, intending to cut off a retreat. Two days later he sent a diversionary force consisting of two corps—roughly 30,000 men under the command of Gen. John Sedgwick—across the Rappahannock below Fredericksburg and crossed upriver with the main body of his army.

Union General Joseph Hooker commanding troops at the Battle of Chancellorsville, May 1863.MPI—Hulton Archive/Getty Images

By May 1 his superior forces were massed near Chancellorsville, a crossroads in a densely forested lowland called the Wilderness. Deprived of his cavalry, however, Hooker was blind to Lee’s movements, and on May 2, when Lee ordered Gen. Thomas J. (“Stonewall”) Jackson’s “foot cavalry” to swing around and attack the Union right, Hooker’s surprised flank was routed. The audacious maneuver, which saw Lee violate basic military doctrine by dividing his forces in the face of a superior enemy, further cemented Lee’s reputation among both friend and foe. The Union general withdrew, and Lee’s pressure over the next three days forced a Union retreat north of the river. The South’s greatest casualty was the loss of Jackson, who was accidentally shot by his own men while returning from a reconnaissance of Union lines. He survived the amputation of his left arm in the field, but infection set in, and he died of pneumonia on May 10. Of 130,000 Union soldiers engaged at Chancellorsville, more than 17,000 were casualties (some 7,500 were killed or reported missing); of 60,000 Confederates, more than 12,000 were casualties (more than 3,500 were killed or reported missing).

Confederate Generals Stonewall Jackson (left) and Robert E. Lee meeting for the last time at the Battle of Chancellorsville, May 1863.Library of Congress, Washington, D.C. (digital file no. LC-DIG-pga-02907)

Message to General Robert E. Lee from Stonewall Jackson, May 2, 1863, during the Battle of Chancellorsville, Virginia. The body of the message reads, “The enemy has made a stand at Chancellor's which is about 2 miles from Chancellorsville. I hope as soon as practicable to attack. I trust that an ever kind Providence will bless us with great success. Respectfully, T.J. Jackson.” Jackson's attack was the turning point of the battle.North Wind Picture Archives